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Murrins Complex - Coolesker/Beragh EskersTyrone
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Summary Full report
Site Type: Inland exposure
Site Status:
District:
Grid Reference: H512650, H508669, H531751
Rocks
Rock Age: Quaternary
Rock Type: Diamict, Gravel, Sand
Interest
Other interest: No data, Ice stagnation, esker

Summary of site:

This area is important for a series of eskers that fed into ice-margin moraines fringing a glacial lake or lakes to the east. Deltas were also created in this process.

Between Beragh and Lough Macrory at Gortnaclare, Annagh, Seefin and Cloghfin there are numerous long and slightly winding ridges up to 1 km long, 10 m high and 40 m wide. They share a general trend which is south west/north east and they feed into and end at north/south trending ridges at Beragh and Coolesker which are considered to be moraines. Flat-topped features (140 m above sea level) at Beragh Hill, Mullaghslin and Drumnakilly are interpreted as esker-fed deltas on the western ice margin of the lake or lakes. The general picture in this area as these features were created is of a lobe of the ice sheet retreating into the Lough Neagh Basin occupying and blocking the Pomeroy Sixmilecross valley to the east, while a second major ice margin with a north/south front was retreating to the west. Massive volumes of meltwater flooded from this melting and deflating ice mass, draining through tunnels in the ice and accumulating to create a temporary lake. Everything from finely pulverized rock flour to large cobbles and boulders released during melting was swept into these tunnels (creating the linear deposits of the eskers) and most passed through to be released into the lake at the ice margin where it either accumulated, heaping along the ice face (creating the moraine) or, where flow was particularly strong, building out into the lake to create the deltas.


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